Apparatus for diminishing magnetic dispersion in electric transformers



Sept. 1, 1925.

J. KUBLER ET AL APPARATUS FOR DIMINISHING MAGNETIC DIsPEIismN IN ELECTRIC TRANSFORMERS Filed June 2, 1921 Patented Sept. 1, 1925.

UNITED STATES 1,551,960 PATENT OFFICE.

JOHANN K'U'BLER AND ROBERT MARGHAND, OF BALDEN, SWITZERLAND, ASSIGNORS To AKTIENGESELLSCHAFT BROWN, BOVERI AND CIE., OF BADEN, SWITZERLAND.

APPARATUS FOR DIMINISHING MAGNETIC DISPERSION IN ELECTRIC TRANSFORMERS.

Application filed June 2,

To all whom it may concern:

Be it known that JoHANN Kiinucn, a citizen of the Swiss Republic, residing at Schlossbergweg, Baden, Switzerland, and ROBERT MAnonANn, a citizen of the Swiss Republic, residing at Kappelerhof, Baden, Switzerland, have invented certain new and useful Improvements in Apparatus for Diminishin Magnetic Dispersion in Electric Transfdrmers, of which the following is a specification. v

For the purpose of regulating the secondary voltage of an electric transformer, with a given constant primary voltage, it has been usual to vary the ratio between the turns of the primary and secondary by breaking and making connection at points of the windings. In this procedure it is generally not possible to avoid a variation. in the magnetic dispersion conditions of the transformer, because the mutual compensation of the working currents of the two windings is disturbed by a variation in the effective number of turns of only one winding.

Figure 1 is a diagram of connections for an ordinary regulable transformer;

Figure 2 is a diagram of connections for a regulable transformer according to the invention;

Figures 3 and 4 show diagrammatieally a transformer constructed according to the invention, feeding a monophaseand a threephase vapour rectifier;

Figure 5 shows a manner of arranging the coils on the core of a transformer arranged according to the invention.

Referring to the accompanying drawings:

If it be assumed in Fig. lffor instance that the control leve H is situated on contact 1 of the contact track connected to the disconnectable turns 01 of the primary P of the transformer T, the current 9' flowing in the secondary S is compensated by the current 2', of the primary circuit, with the exception of a small amount corresponding to the excitation of the main and stray field.

If now by rotating the lever H the portion (Z of the primary be disconnected, then only the currents in the portions (1: and c of the windings will compensate each other; whereas the secondary current 2' in the turns 12 will operate to generate a field, because there are no ampere turns for com- 1921. Serial No. 474,549.

pensating this portion of the. winding This generated field is nevertheless a dispersion field and is not well interlinked with that part c of the primary circuit which happens to be effective, and therefore mainly represents a stray field. The cutting out of the winding (1 renders the secondar voltage of the transformer dependent in a high degree upon the load.

This dispersion is therefore injurious, and the present invention has for its object to provlde an improved apparatus for diminishing the dispersion in transformers that are adapted to be regulated by disconnectmg and connecting some of the turns. In this improved apparatus the portions of the one winding that are situated opposite the disconnectable and non-disconncctable portions of the other winding, are connected in parallel with each other.

In this arrangement the winding that is situated opposite the disconnectable portion of the winding, is traversed only by a" part current '5 which is smaller the greater the number of turns that are disconnected on the opposite side, and drops finally to zero, provided that the constant portion of the other winding is present. This disappearance of the part current has the result that, after a complete disconnection of the regulable portion of the winding, the magnetic dispersion of the transformer is approximately the same as it was when a l the turns were connected.

The invention will now be further explained with reference to the constructional example illustrated in Fig. 2 wherein the reference letters have the same significance as in Fig. 1. Here again the primary P is composed of the invariable portion 0 and the regulable portion d.

Opposite the portion 0 is the secondary a; and opposite the portion (1 is the secondary 7/; the arrangement being such that (zis well interlinked with c, and 7) is well interlinked with (Z. The windings (I- and 7) have the same number of turns and are connected in parallel with each other. ()f the secondary current i the portion z' traverses the winding n, whilst the other portion i traverses the winding 6.

When the lever II is on the contact 1. the primary current will flow through the parts 0 and d of the winding, which are in series. Secondary current will be distributed over the two windings'a and b in such a manner that the ampere windings of a are compensated by the ampere windings of c and those of b by the ampere windings of cl, all but a remainder necessary for the production of the main fields. The stray fields are small, as the interlinking of the opposite parts of the winding is good.

When the lever His on the contact 6 the primary current will flow only through the part c of the winding. Secondary current will flow correspondingly mostly through the winding a while only a small current will flow through the winding 5, owing to the increase of its self-induction. In this position as well the windings a and c, which carry the main part of the current, are well interlinked and hence the drop in voltage is only small. This is effected by the wind ings a and I) being connected in parallel, which permits of any proportion between the current 2' and 2' This constitutes the difference and the improvement as compared with the arrangement shown in Figure 1. In the intermediate positions ofll the advantage of the independent current setting is less apparent but is still present. The inductive voltage drop of the regulating transformer of Figure 2 will, therefore, be smaller in all circumstances than that according to Figure 1.

Fig. 3 illustrates the case where the improved apparatus is used for feeding a mono-phase rectifier. The primary P of the transformer T is connected to the alternating current supply circuit N,. The winding a is provided with a central lead 1 constituting the negative main of the direct current supply circuit N The anodes A and A are fed through the leads 1' and 1" in parallel from the windings a and b. This construction allows also an advantageous arrangement of the windings on the iron core of the transformer.

Generally in the case of cylinder windings, it is sought to make the primary the inner cylinder, and to make the secondary the outer cylinder (or vice versa). That construction has in the case of regulable transformers the great drawback that either the disconnectable coils of the primary, or the secondary coils that are in many cases connected together in parallel, are situated on the inner cylinder, that is to say, are inaccessible. In the apparatus according to the invention, however, the secondary is composed of the two parallel portions (1 and b, of which I) has no complicated internal connections, since it carries practically only a relatively small part current. In the improved apparatus therefore it is feasible to arrange the coils on the iron core F in the manner illustrated in Fig. 5. The inner menace cylinder consists of the invariable'portion c' of the primary and the secondary I) which is situated opposite the disconnectable portion (1? of the primary. The outer cylinder on the contrary consists of the secondary a and the disconnectable portion (2 of the primary. The parts constituting the outer cylinder are well accessible in this construction, and their manufacture, connections and supervision are considerably facilitated.

An application of this apparatus to polyphase installations is illustrated in Fig. 4.

In this Fig. 4 :N is the three-phase supply circuit to which the three-phase transformer T is connected. The primary consists of the three phase windings P P P P and P P of which P P and P represent the constant, and P P and P represent the regulableportions of theprimary. The secondary portions are so arranged that the secondary portions S S 8., are situated opposite the primary portions P P and P and the secondary portions 8,, S S, are situated opposite the primary portions P P and P the windings S 2 and S being connected in parallel with their res ective corresponding windings S S an S and have a common zero point 0.

This zero point 0 is connected to the negative main of the direct current supply circuit N, the positive main of which is connected to the cathode K of the rectifier G. The anodes A A and A are connected to the free ends of the secondary windings. In this case also the inductive voltage drop of the transformer will be considerably less than is the case in the usual construction hitherto employed.

What we claim is 1. A transformer comprising a first winding having a regulable portion and a second winding having two portions connected permanently in parallel, the re lable portion of the first winding being ocated exactly opposite one portion of the second winding and the nonaegulable portion of the first winding being located opposite the second portion of said second winding.

2. A transformer as claimed in claim 1, wherein the non-regulable portion of the first winding and the portion of the second winding that is opposite the regulable portion of the first winding is arranged as an inner cylindrical winding surrounded by an outer cylindrical winding comprising the regulable portion of the first winding and the remainmg portion of the second winding.

In testimony whereof we have signed our names to this specification.

JOH. KIJBLER. R. MARCHAND. 

